I. Field of the Invention
The present invention relates generally to satellite communication systems, and more particularly, to an apparatus, system, method, and computer program product for providing a flexible ringer to announce an incoming telephone call.
II Description of the Related Art
A variety of multiple access communication systems and techniques have been developed for transferring information among a large number of system users. However, spread spectrum modulation techniques, such as code division multiple access (CDMA) spread spectrum techniques, provide significant advantages over other modulation schemes, especially when providing service for a large number of communication system users. The use of CDMA techniques in multiple access communication systems is disclosed in U.S. Pat. No. 4,901,307, which issued Feb. 13, 1990, entitled Spread Spectrum Multiple Access Communication System Using Satellite Or Terrestrial Repeaters, and U.S. Pat. No. 5,691,974, which issued Nov. 25, 1997, entitled Method And Apparatus For Using Full Spectrum Transmitted Power In A Spread Spectrum Communication System For Tracking Individual Recipient Phase Time And Energy, both of which are assigned to the assignee of the present invention, and incorporated herein by reference.
The above referenced patents disclose communication systems in which a large number of generally mobile or remote system users or subscriber units ("user terminals" or "mobile stations") employ at least one transceiver to communicate with other user terminals, or users of other connected systems, such as a public telephone switching network. Communication signals are transferred either through satellites and gateways, or directly to terrestrial base stations (also sometimes referred to as cell-sites or cells).
One type of remote user is a fixed unit, such as a wireless phone, facsimile device, and so forth, in a remote location where wirelines are impractical, such as an offshore oil rig or other remote geographical location. Such remote locations often require that multiple phones be serviced by a single access channel or communications link from a satellite in a "party line" type of service. A party line is a single communications path or link that is used as a shared resource. The defining feature of party line service is that a telephone call can be answered or initiated by a user at one party line phone, and all other party line phones can participate in the telephone call. But, an additional telephone call by a non-participating phone cannot be effected until the first call is terminated.
An exemplary situation would be a telephone call between workers on an offshore oil rig and land-based vendor technicians, where the purpose is to solve a technical problem. It would be advantageous for workers at multiple locations on the oil rig to be able to simultaneously participate in the telephone call. A party line generally having a single access address, code, or telephone number can meet this need. The access address, code, or telephone number could also be referred to as a communications system address, user terminal (UT) address, UT ID, etc.
Another situation in which multiple phones may be required is in a remote geographical land location where it is not cost effective to run standard telephone lines. These may include mid-desert locations, small island locations, rural-third world locations, and the like. In those cases, a community building having multiple rooms, might be set up with phones in each room. Another example would be a remotely located multi-family dwelling, where each family (or business) would want to have a phone. In many of these cases, it would not be cost effective to install separate satellite receiving equipment for maintaining separate communication links for each phone. In each of these cases, a party line arrangement would provide a cost effective method of maintaining efficient telephone communication links.
A remote location with party line service can be efficiently linked to a satellite communications system through a radio antenna unit (RAU). An RAU is a transceiver, comprising well known elements, that transmits and receives a modulated carrier signal to and from the satellite communications system through an antenna. During transmission, the RAU accepts audio signals from the multiple phones. An audio coderdecoder (or audio codec) in the RAU digitizes the audio signals, which are then used to modulate the carrier signal that is radiated to a satellite (or other relay apparatus) by the antenna. During reception, the RAU receives an input signal comprising a modulated carrier signal from a satellite. The RAU demodulates the input signal to retrieve the digital audio signal. After which, the audio codec converts the digital audio signal to an analog audio signal, and causes the analog audio signal to be sent to the multiple phones.
When the audio signals are primarily composed of human speech, a vocoder may be used to compress (de-compress) the digital bit stream before (after) the carrier signal is modulated (de-modulated) to make more efficient use of the carrier signal bandwidth. The vocoder operates on the principle that speech sounds can be predicted and extrapolated based on the analysis of a small portion of a sound. Thus, the vocoder removes selected bits from the digital bit stream before carrier signal modulation, and adds them back after de-modulation. Vocoders are especially useful in wireless communications systems where multiple user or subscribers are competing for limited carrier signal bandwidth.
The above described communications system requires a ringer to notify the phone users of an incoming call so the users can answer or "pick-up" the incoming call. Remote users are by definition capable of being scattered around the entire world, and their expectations of a ringing telephone varies depending on their geographic location. For example, a phone user in India expects a ringing telephone to sound different from a phone user in Brazil or Australia. This is primarily the result of the variation in ringer frequencies and patterns used by geographically diverse service providers. In other words, service provider territories generally terminate at national or geo-political boundaries, and thus ringer frequencies and patterns often change at these boundaries.
A conventional ringer for a POTS (Plain Old Telephone Service) wireline system sends a large AC voltage from a central office over a telephone cable to a phone. The AC voltage is typically 70-90 volts at 15-20 Hz and drives an electromechanical bell ringer that produces the ringing sound. When a user picks-up the receiver a DC loop is formed and a small DC current begin to flow from the central office. The central office detects the DC current flow and terminates the AC voltage driving the bell ringer.
A conventional ringer for a mobile phone, and some fixed phones, is based on a piezo-electric device that generates an audible tone when pulsed by an electrical signal. The mobile phone senses an incoming call and pulses the piezo-electric device, which generates an audible tone that alerts the mobile phone user of an incoming call. Piezo-electric devices are not flexible, that is, they generate audible tones within a narrow frequency range. In order to change operation from one audible tone to another, an existing mobile phone must be fitted with a physically different piezoelectric device.
Both the conventional POTS ringer and the piezo-electric ringer are inappropriate choices for the remote user served by the satellite communications system described above. A conventional POTS ringer is inappropriate because the satellite system is by definition wireless. Thus, there is no telephone cable from the central office with which to carry the AC voltage that drives the electromechanical bell.
The piezo-electric device is inappropriate because it is too inflexible, and different use-areas or regions often use entirely different audible tones or signals for announcing an incoming call. If a piezo-electric device were used, the location of each remote user would have to be known prior to manufacturing the phones in order to install the proper piezo-electric device. This information is unlikely to be available at the time of manufacture, and the manufacturing cost associated with carrying multiple piezo-electric devices would be prohibitively expensive even if it was available. What is needed is a flexible ringer for use with a satellite party line phone system serving users at variable geographic locations.
The preceding discussion focused on the motivation for a flexible ringer in a party line phone system. A flexible ringer would also be useful for a single line configuration (i.e. one phone per phone number, UT address, or UT ID) where the phone could be used in variable geographic locations. The phone could be stationary or mobile (or portable), and the flexible ringer would enable the ringer sound to be customized to satisfy the local ringer requirements for multiple geographic locations. For example, the ability to customize the ringer sound would be useful to a phone manufacturer that is uncertain of the final destination of each phone at the time of it's manufacture. A flexible ringer would permit a service provider to select a ringer sound upon delivery of a shipment of phones.
Furthermore, a flexible ringer would allow an individual phone user to customize the ringer sound as desired, independent of any geographic location. If the phone is transferred to a second user, the second user may also adjust the ringer sound as desired, and so on for multiple serial phone users.